1) Field of the Invention
The present invention relates to a technology for image processing, and more particularly a method of, an apparatus for, and a computer program for an image processing in a digital color copier, a color printer, a color facsimile machine, and the like.
2) Description of the Related Art
A technology known as the image area separation is currently in use for image processing in digital a color copier, a color printer, a color facsimile machine, and the like. The image area separation is a process in which pixel areas of an image being scanned are recognized as a character area or an intermediate tone area of a picture, etc. and an image area separation data (attribute information) is created for each pixel. Appropriate processes for the character areas and the intermediate tone areas are carried out with a help of the image area separation data. For instance, based on the image area separation data, a space filtering process may be carried out to enhance a resolution of the character area, or an intermediate toning process may be carried out to enhance a contrast of the intermediate tone area.
A color image that is output from the digital color copier is obtained by superposing four color plates, K (black), C (cyan), M (magenta), and Y (yellow). In order to control a printing timing of the different color plates, the image needs to be stored once in memory. However, to avoid occupation of too much memory, a method is adopted by which image data is compressed before being storing in a memory. Recently, there has been a rising demand to not only be able to obtain an output of a scanned image output, but also to be able to store the image as a digital data, to be output whenever required, obviating a need for an original document for a subsequent copies, or to be used on a personal computer (PC), and the like. For these purposes as well, the image data needs to be compressed to an appropriate size. It has therefore become common in the image processing of the digital color copier to incorporate a step of compressing the image data and storing the data in the memory.
FIG. 10 is a block diagram of a flow of image processing of a copier. As illustrated in FIG. 10, a compression process and a decompression process take place between a filtering process and a color correction process. The processes involving the image area separation data are the color correction process and the intermediate toning process, both of which take place after the compression process. Therefore, it is necessary for a timing of the image area separation data to coincide with a timing of the image data. For instance, an image processing apparatus that is disclosed in U.S. Pat. No. 3,134,756 includes an image area separating unit that separates an input image data into a binary image area composed of a character or a line data and an intermediate toner image area composed of a picture or a halftone print, etc. A first image processing based on the image area separation data is then carried out. The image data and the image area separation data are then compressed and stored. The stored data are then decompressed. Based on the decompressed image data, a second image processing is then carried out on the decompressed image data. As described in U.S. Pat. No. 3,134,756, as the timing of the image area separation data coincides with the timing of the image data, the image area separation data is also compressed once and stored in the memory.
If scanned image data is to be transferred as a digital data to the personal computer (PC), instead of being output on a paper, any data at any stage of the processing can be transferred. However, it would be ideal if the image data that is transferred to the PC is the image data that is compressed and stored in the memory. The name of the image data thus transferred may be edited on the PC and may also be output on a paper. In order to be able to obtain an output on a paper, the edited data, which has been processed only up to the compression stage, must once again be entered in the memory so that the image quality is identical with that of a normal copier system. However, once an image that is transferred to another device and is read again loses its image area separation data (attribute information). Consequently, a process switching based on the image area is not possible, resulting in inferior image quality. Even if the image area separation data (attribute information) is created again for the image data that has been transferred to an outside device and scanned again, the separation accuracy would be low as compared to the image area separation data (attribute information) of the original image due to a fact that the image data has been compressed.